In a machine tool equipped with a numerical control device, machining is performed by commanding spindle rotating speed from a machining program. In the machine tool, machining cannot be performed during the period from the commanding of the spindle rotating speed until actual spindle rotating speed reaches the commanded rotating speed. Therefore, a waiting time occurs and a machining time becomes long. However, with such a numerical control device, it is unnecessary for every command to wait for the spindle rotating speed to reach commanded rotating speeds. For example, in the case of a cutting command, it is necessary to wait for the spindle rotating speed to reach a commanded rotating speed. However, in the case of the non-cutting command such as a positioning command, it is unnecessary to wait for the spindle rotating speed to reach rotating speed commanded. The determination for each command as to whether to wait or not can be done by making a ladder. However, because the ladder is complicated, it is not easy for an operator to modify the ladder.
For example, Patent Literature 1 discloses a technology that uses a machining program in a control device to command and select whether the next block is executed after waiting for spindle rotating speed to reach commanded rotating speed or whether the next block is executed even if the spindle rotating speed has not reached the commanded rotating speed.
Patent Literature 2 discloses a technology used in a numerical control device to control the timing of the output of a spindle rotating command such that the spindle rotating speed reaches commanded rotating speed according to a timing when a cutting command is started.